In an air conditioning unit (heating ventilation and air conditioning unit; HVAC unit) of a vehicle air conditioning device, an evaporator, a heater core, an air mixing damper, a plurality of blow-off mode switching dampers, and the like are incorporated inside of a unit case in which an air flow channel is formed. In general, the unit case is configured by integrally coupling a plurality of divided resin cases, in consideration of restrictions on shaping and the incorporation of the above-mentioned machines.
These divided cases are coupled integrally to each other through a mating portion, and the mating portion is configured by fitting a convex portion provided on a division end surface of one divided case to a concave portion provided on a division end surface of another divided case. This configuration can prevent air leakage and water leakage from the coupled portion. Even if the divided cases are coupled to each other through the mating portion, however, water may invade due to a capillary action, and water leakage may occur. Under the circumstances, PTL 1 to PTL 4 disclose, for example, techniques of: interposing an elastic seal member; providing a stepped portion that blocks water from invading a division end surface; and providing a cover wall that covers at a given interval a division end portion in which a mating portion is formed.